PROJECT SUMMARY Acute kidney injury (AKI) is a growing public health burden. The syndrome itself is occurring in more diverse contexts and the long-term sequelae of AKI include chronic kidney disease (CKD). More than ever then, AKI research must identify candidate pathways that can be assessed and targeted in humans. In the first four years of this award, the applicant's laboratory has found that the mitochondrial biogenesis regulator, PGC1? (PPAR?-coactivator-1?), confers robust resistance to simple, common acute stressors that culminate in AKI such as acute systemic inflammation and renal ischemia. Moreover, we have observed that renal PGC1? expression is markedly suppressed in human AKI. Finally, we have implicated a novel downstream effector pathway for PGC1??biosynthesis of the energy carrier nicotinamide adenine dinucleotide (NAD+). Based upon these results, we hypothesize that the PGC1?-NAD+ pathway may be a critical determinant of metabolic defense against diverse renal tubular insults. To test this concept in ways that advance both our fundamental understanding of this emerging candidate and that catalyze translational efforts, we propose three parallel aims: (1) identify when in the CKD-AKI spectrum tubular PGC1? induction is most beneficial; (2) critically evaluate the role of NAD+ biosynthetic pathways in experimental AKI downstream of PGC1?; and (3) dissect the relative contributions of mitochondrial biogenesis versus NAD+ biosynthesis in the metabolic protection conferred by PGC1?. To accomplish this, our team is composed of individuals possessing complementary expertise with a proven track record of collaborating to investigate metabolism in AKI. We have developed a suite of tools ranging from metabolomics and lipidomics applications to gene-edited cells to function- ultrastructure analysis of mitochondria. The output from the proposed aims will advance our understanding of how renal tubular metabolism bridges CKD and AKI; identify specific contexts in which PGC1?-NAD+ should be pursued clinically; and deepen our fundamental understanding of PGC1? and NAD+ in renal health. In concert with a growing number of outstanding groups investigating renal metabolism, it is our hope that the proposed studies help expand this new frontier in renal biology.